Paroxetine is indicated for treating various types of depression disorders, including depression with anxiety and reactive depression. The chemical name of paroxetine is trans-(-)-3-[(1,3-benzodioxol-5-yl-oxy)methyl]-4-(4-fluorophenyl)piperidine with the following structure:

and a compound of formula III below is an intermediate commonly used for synthesizing paroxetine,

Paroxetine can be prepared from the compound of the formula III according to the method provided in WO2009005647 A2, which provides a reaction scheme shown below:

The methods for preparing the compound of the formula III as disclosed in the existing literature generally include the following two methods, for example:
The Journal of Fine Chemical Intermediates, 2007, 37(3), P41-44 discloses a method for preparing a racemic compound of the formula III, including reacting ethyl 4-fluorocinnamate with ethyl 3-(methylamino)-3-oxopropanoate to obtain the racemic compound of formula III, and the racemic compound of the formula III needs to be resolved to obtain an optically pure compound of formula III, which has a great loss in raw materials, resulting in an increase of cost.
Tetrahedron: Asymmetry 22 (2011) 1-3 discloses a method as shown below:

In this method, firstly a chiral amide, i.e. (R)-3-(3-(4-fluorophenyl)acryloyl)-4-phenyloxazolidin-2-one is obtained by reacting a chiral auxiliary, i.e., (R)-4-phenyl-2-oxazolinone, with p-fluorocinnamic acid, and then the compound of formula III is obtained through conjugate addition and cyclization between the chiral amide and ethyl 3-(methylamino)-3-oxopropanoate in the presence of sodium hydride. Sodium hydride is inflammable and explosive, requires rigorous reaction conditions, and hence is unfavorable to large-scale industrial production. Moreover, the product obtained through repeating the route by the skilled person according to the method provided in the examples has a poor optical purity and a low yield.
Therefore, there is a need for developing a new synthesis process for preparing the compound of formula III, so as to meet the demand of larger-scale industrial production.